Introduction

Uses for Prilocaine Hydrochloride

Dental Anesthesia

Prilocaine Hydrochloride Dosage and Administration

General

Determine dosage based on anesthetic procedure, depth of anesthesia, area to be anesthetized, vascularity of oral tissues, physical condition of the patient, and individual patient response.ac Use smallest dose required to produce the desired effect.a

Administration

Injection

Administer by infiltration or by nerve block.a

Consult specialized references for specific techniques and procedures of administration.ab

Aspirate prior to administration to guard against intravascular injection.c

For maxillary infiltration for short procedures that can be completed within 15 minutes (e.g., procedures involving maxillary anterior teeth), use prilocaine hydrochloride 4% solution without epinephrine.c For long procedures or those involving maxillary posterior teeth, use prilocaine hydrochloride 4% solution with epinephrine 1:200,000.c

For inferior alveolar block, may use prilocaine hydrochloride alone or in fixed combination with epinephrine; no practical clinical differences between these preparations.c

For chemical disinfection of the cartridge unit, use isopropyl (rubbing) alcohol (91%) or ethyl alcohol (70%).c Do not use brands that are not of USP grade, since these preparations may contain denaturants that may be injurious to rubber.c Because certain metallic ions (e.g., mercury, zinc, copper) have been associated with swelling and edema following local anesthesia, do not use chemical disinfectants containing or releasing these ions.c Do not autoclave because solutions of epinephrine and the closures employed in cartridges cannot withstand autoclaving temperatures and pressures.c

Dosage

Available as prilocaine hydrochloride and as fixed combination containing prilocaine hydrochloride and epinephrine bitartrate.c Dosage expressed in terms of prilocaine hydrochloride.c

Pediatric Patients

Dental Anesthesia

Infiltration, Nerve Block

Children <10 years of age: 40 mg (1 mL) of prilocaine hydrochloride 4% solution (with or without epinephrine) is adequate for a procedure involving 1 tooth, 2–3 teeth (maxillary infiltration), or teeth in an entire quadrant (mandibular block).ac

Prescribing Limits

Pediatric Patients

Dental Anesthesia

Infiltration, Nerve Block

For children <10 years of age with normal lean body mass and normal development, maximum dose is determined using standard pediatric drug formulas (e.g., Clark’s rule).a For example, dosage for a 5-year old child weighing 50 lbs should not exceed 150–200 mg (6.6–8.8 mg/kg or 3–4 mg/lb).c

Special Populations

Hepatic Impairment

Geriatric Patients

Other Populations

Reduce dosage in debilitated or acutely ill patients and in patients with arteriosclerosis or occlusive arterial disease.bc

Cautions for Prilocaine Hydrochloride

Contraindications

Congenital or idiopathic methemoglobinemia.a

Known hypersensitivity to prilocaine or other local anesthetics of the amide type.ab

Warnings/Precautions

Warnings

Experience of Supervising Clinician

Should be used only by clinicians who are sufficiently knowledgeable in the diagnosis and management of dose-related toxicity and other acute emergencies that might arise.c Oxygen, resuscitative equipment, and drugs must be available for immediate use.abc Delay in proper management of dose-related toxicity may result in acidosis, cardiac arrest, and, possibly, death.b

Methemoglobinemia generally is dose related but may occur at any dose in susceptible individuals.c Methemoglobin concentrations <20% generally do not produce any clinical symptoms; however, if cyanosis occurs within 2–4 hours after injection, evaluate general health status of patient.c Other manifestations of methemoglobinemia may include tachycardia, fatigue, headache, lightheadedness, and dizziness.a

Carefully monitor cardiovascular and respiratory vital signs after each local anesthetic injection.c

Failure to recognize early manifestations of depressed cardiovascular function (e.g., sweating, feeling of faintness, changes in pulse or sensorium) may result in progressive cerebral hypoxia and seizure or serious cardiovascular catastrophe.c To manage cardiovascular depression, place patient in recumbent position and ventilate with oxygen.c May require administration of IV fluids and/or a vasopressor (e.g., ephedrine) depending on clinical presentation.c

Use with caution in patients with impaired cardiovascular function, severe shock, or heart block.c

Some prilocaine hydrochloride preparations contain epinephrine; risk of exaggerated vasoconstrictor response in patients with peripheral vascular disease or hypertensive vascular disease.c Use with caution in areas of the body supplied by end arteries or having otherwise compromised blood supply.c

Familial Malignant Hyperthermia

Many drugs used during the conduct of anesthesia may trigger familial malignant hyperthermia; not known whether amide-type local anesthetics may trigger this reaction.c However, standard protocol for management should be available.c Early unexplained signs of tachycardia, tachypnea, labile BP, and metabolic acidosis may precede temperature elevation.c If familial malignant hyperthermia is confirmed, discontinue triggering agent and initiate appropriate therapy (e.g., oxygen, dantrolene) and other supportive measures.c

Risks Associated with Administration

Small doses of local anesthetics injected into the head and neck area (including retrobulbar, dental, and stellate ganglion blocks) may produce adverse reactions similar to systemic toxicity seen with unintentional intravascular injections of larger doses.c Confusion, seizures, respiratory depression and/or respiratory arrest, and cardiovascular stimulation or depression reported.c Monitor circulation and respiration in patients receiving these blocks.c

Potential for life-threatening adverse effects (e.g., irregular heart beat, seizures, breathing difficulties, coma, death) when topical local anesthetics are applied to a large area of skin, when the area of application is covered with an occlusive dressing, if a large amount of topical anesthetic is applied, if the anesthetic is applied to irritated or broken skin, or if the skin temperature increases (from exercise or use of a heating pad).101102

Lidocaine 4% gel has been investigated to reduce discomfort during mammography.101103 Whether such use could result in serious reactions has not been determined.101103 Patients should speak with their clinician if they are considering using a topical anesthetic before obtaining a mammogram.101

When a topical anesthetic is needed for a procedure, use of an FDA-approved preparation has been recommended.k Use a preparation containing the lowest concentration of anesthetic likely to be effective; apply a small amount of the preparation to the affected area for the shortest period necessary for the desired effect,k and do not apply to broken or irritated skin.101

Use of Fixed Combination

When used in fixed combination with other agents, consider the cautions, precautions, and contraindications associated with the concomitant agents.

Specific Populations

Pregnancy

Category B.c

Lactation

Not known whether prilocaine is distributed into milk.a Caution if used in nursing women.c

Duration

Following maxillary infiltration with 4% prilocaine solution without epinephrine, pulp anesthesia persists for 10–15 minutes,ac which provides complete anesthesia for procedures lasting an average of 20 minutes.c Average duration of soft tissue anesthesia is approximately 2 or 2.25 hours following infiltration with 4% prilocaine solution without or with epinephrine, respectively.c

Following inferior alveolar nerve block, average duration is approximately 2.5 or 3 hours with 4% prilocaine solution without or with epinephrine, respectively.ac

When used for infiltration or nerve block without epinephrine, duration of anesthesia is longer than that of an equal dose of lidocaine.a When epinephrine is added to both drugs, duration of anesthesia of lidocaine is lengthened to a greater extent than that of prilocaine.a

Distribution

Extent

Local anesthetics are distributed to all body tissues.b

Crosses blood-brain and placental barriers.a

Not known if distributed into milk.a

Plasma Protein Binding

At concentrations of 0.5–1 mg/mL, approximately 55% of drug is bound.c

Elimination

Metabolism

Systemically absorbed prilocaine is metabolized principally in the liver to o-toluidine and l-N-n-propylamine;ao-toluidine found to produce methemoglobin (see Methemoglobinemia under Cautions).c Some metabolism also may occur in the kidneys.a

Elimination Route

Excreted in urine as various metabolites; <1% excreted as unchanged drug.a

Stability

Storage

Parenteral

Injection

Actions

Local anesthetics block the generation and conduction of nerve impulses by increasing the threshold for electrical excitability, slowing the propagation of the nerve impulse, and reducing the rate of rise in the action potential.bc

Produces less vasodilation than an equal dose of lidocaine hydrochloride.a

Some preparations formulated with epinephrine to decrease prilocaine’s rate and extent of systemic absorption and to prolong its duration of action.ab

Has intermediate duration of action.ab

Advice to Patients

Prior to administration, advise patients of the possibility of temporary loss of sensation and muscle function following infiltration or nerve block injections.c

Advise patients to avoid inadvertent trauma to the lips, tongue, cheek mucosae, or soft palate when these structures are anesthetized; postpone ingestion of food until normal function returns.c

Advise patient to consult dentist if anesthesia persists or if rash develops.c

Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses (e.g., cardiovascular or liver disease).c

Importance of women informing their clinician if they are or plan to become pregnant or plan to breast-feed.c

Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.